hemodynamic interactions Flashcards
what are venous compartments separated into?
Peripheral and central
What is crucial for determining how well a cv system is operating?
Cardiac filling pressure
What is very sensitive to small changes in pressure?
EDV
How much does it take to fill the circulatory system. No pressure or stretching?
3.5liters
What are the 2 things that affect the mean circulatory filling pressure?
- circulating blood volume
2. state of peripheral venous tone
What is the amount of contents in the peripheral venous compartment?
2.5 liters
which with increase tone is added to the circulatory system!
Would arteries of capillaries affect other compartments with the necessary pressure?
No, their volume is small and would have a negligible effect on mean circulatory filling pressure
Does the presence of flow to the circuit change the total volume or mean circulatory filling pressure?
NO
- flow induced distribution
- PVS usually close to mean circulatory filling pressure
Which is more compliant veins or arteries?
Veins. Added blood doesnt affect pressure much
** Veins 50x more compliant
Arteries, pressures affected greatly by adding blood to arterial system
With flow does pressure in the peripheral venous system change much?
Nope
Flow or now flow doesnt affect mean filling pressure
What is a good indicator of the circulatory status?
Central venous pressure
- CV system adjusts operation continually to meet changing metabolic demands
Is the CV system closed or open? What are the consequences of this?
Closed
- change in pressure in one area affects pressure, flow and volume throughout the circuit
What consists of the central venous compartment?
Great veins of thorax and right atrium
What is venous return?
Rate at which blood is coming back to the central venous compartment
- should match cardiac output
What happens when CO doesnt match venous return?
Volume of central venous compartment must be changing
Produces change in central venous pressure
What is the role of CVP?
always driven to a value that makes Cardiac output = venous return
what essentially is the same thing as peripheral venous pressure?
Mean circulatory filling pressure
PV and CV compartment must equal the same
Q=^P/R
What are the 2 influences of peripheral venous pressure?
- Changes in blood volume (increase in volume in a fixed compartment increases pressure)
- Changes in venous tone (vasoconstriction via sympathetics)
When central venous pressure decreases what happens to venous return?
increases
inverse relationship
If pressure diff between CV and PV compartment determining venous return then??
Increase peripheral venous pressure works just as well as dropping central venous pressure on increasing venous return.
When are CO and VR equal to one another?
at central venous pressure of 2 mmHg
both affected by central venous pressure
What determines where the cardiac and venous function curves intersect?
Heart and peripheral vasculature
DO cardiac sympathetics affect the venous function curve?
NO
What is the hallmark of of CHF?
Very high central venous pressure
What does high central venous pressure do to a CVP CO/VR curve?
Right shift
What results in a left shift of the CVP CO/VR curve?
Low central venous pressure
What is mean circulatory filling pressure?
Hypothetical pressure related to filling of the the whole systems vasculature without stretching any of its walls or developing any internal pressure.
- Filling of the anatomical space
How much volume of blood do we have? How much more is this than the volume to fill the entire anatomical circuit? What would the pressure be with increased volume? (equation used)?
a. 4.5l
b. 1000
c. C=^V/^P thus P=^V/C–> P=1000/140=
- 7mmHg–> mean circ filling pressure or pressure that would result in the absence of flow!
